1. Field of the Invention
The invention relates to an envelope for holding transparencies used in overhead projectors. Specifically, the envelopes include at least one opaque flap attached to the envelope using an adhesive tape having increased flexibility.
2. Description of the Related Art
Business presentations, lectures and the like often are augmented by the use of imaged transparencies, which are exhibited to the viewers on a screen by means of an overhead projector (OHP). The individual transparencies are delicate, and easily damaged in storage or transit. Various types of covers, folders and envelopes have been provided in order to enable professional presentations, as well as interim protection of the transparencies.
U.S. Pat. No. 3,875,693 discloses the framing of a transparency in a frame made from carton, paperboard and the like. The frame is meant to mask the illumination gaps formed about the peripheral of the transparency proper. The frame can also be used to make notes or other memoranda needed by the lecturer which remain unseen by the audience. However, these frames are bulky and will not fit into standard size files, binders and shelves, being therefore difficult to store and transport. Also, they are not easily removable without destruction of the frame and attendant damage to the transparency. Finally, the frames are not convenient to attach to transparencies as each one must be carefully positioned and attached by hand.
Swedish Patent Application No. 382,266 discloses an envelope which is a plastic sheet pocket having punched holes along one side, and being open at the top for insertion of the transparency to be presented. These envelopes are removable, simple to handle, store and transport as the outer dimensions are those of standard binders or files. Moreover, the transparency is protected by the envelope and at the presentation, notes can be made on the envelope.
The disadvantage of this envelope is that peripheral illumination is not masked and the lecturer cannot make written notes on the envelopes without having these notes being shown on the screen as well. The punched holes also show an outline on the screen. Therefore, this envelope does not yield a presentation having an extremely professional appearance.
U.S. Pat. Nos. 3,253,358; 3,264,936; 3,438,702; 3,438,703; 3,524,703; 3,536,393; 3,537792; 3,544,211; 3,600,079; and Swedish Patent Application No. 346,166 describe further examples of covers or envelopes for OHP transparencies. The covers and envelopes disclosed in these publications are complicated and difficult to handle and have many drawbacks, e.g., most of these presuppose that the transparencies are to be presented in a prescribed order and the covers of most of these transparencies are difficult to remove.
U.S. Pat. No. 4,810,544 discloses another transparent sleeve comprising a transparent sheet material having a single fold dividing the sheet into two halves, and a strip of double coated adhesive tape running the length of an edge of the sheet substantially parallel to the fold. When folded, the single sheet forms a sleeve. This envelope protects the printed media, and can be stored in a binder when holes are punched along the edge, but again, any written notes or prompts will be visible on the screen.
U.S. Pat. No. 4,402,585 discloses an envelope for overhead transparencies that overcomes many of the disadvantages of the previously described envelopes. The envelope comprises a rectangular pocket formed of transparent sheet material defining opposed rectangular faces which are separable along at least one side edge for insertion of the transparency therebetween. At least one opaque flap is attached in a foldable manner along one of the longitudinal side edges of the pocket. The flap is attached to and spaced a distance from the longitudinal edge such that in the unfolded position the flap extends beyond the side edge and covers the longitudinal edge. In the folded position, the flap exposes the longitudinal side edge. Holes may be punched along the side edge of the material to permit storage of the envelope in a binder, file or the like. Preferably, the flaps are formed of a plastic material which accepts written text by conventional writing instruments.
When stored, the flaps are in the folded position, and are unfolded for use. The means of attachment must allow the flaps to stay in the unfolded position during presentation. Otherwise the flaps might tend to spring back to their folded position, which is inconvenient for the presenter, and may cover the added notes. To aid the situation, the envelope can be placed with the flaps face down on the overhead projector stage, so that the weight of the envelope and the overhead transparency can insure that the flaps stay unfolded. However, where flaps are difficult to fold, the envelope will not lay flat on the stage, which can cause focusing problems, which are especially severe when one uses a reflective type overhead projector. In addition, due to the operating temperature of the OHP and stage, the adhesive used to attach the flap can be transferred to the stage, causing unsightly spots on the screen and messy blotches on the stage which can also transfer to materials used thereafter.
The present inventors have discovered that, by using a certain combination of backing film and adhesive, the flaps can be securely attached to the transparent envelope, easily remaining in either the folded or the unfolded or open position. This obviates the need to turn the envelopes face down on the stage. Further, with the preferred composite tapes, the envelopes can be turned face down and lay flat on the stage with minimal adhesive transfer.